lysine-dev/okhttp ? reverse-engineered prompt

Build me a polished HTTP client library for Kotlin that works well on JVM, Android, and GraalVM.

I want it to feel simple to use, with a fluent request builder, immutable request and response objects, and support for both blocking calls and async callbacks. It should handle the basics really well, including GET and POST requests, headers, request bodies, redirects, transparent compression, connection reuse, caching, and solid error handling when the network is flaky. Please include support for modern HTTP features like HTTP 2, TLS 1.3, certificate pinning, and WebSocket support, plus a small testing helper so I can simulate servers in tests.

Make it production ready and well organized, with examples and clear docs. If anything needs current setup details or best practices, look up the latest docs online before implementing it.